typelevel

cats

Scala2016–2021

typelevel / cats

cats

Lightweight, modular, and extensible library for functional programming.

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6Distinct people

7Mentions

0Explicit recommenders

5.5KGitHub stars

REPOSITORY AT A GLANCE

What to know before exploring

What it is

Lightweight, modular, and extensible library for functional programming.

GitHub

Where it is used

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What people are saying

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Also in these discussions

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This week on Hacker News

Nov 8–Nov 15 UTC · Direct repository links and separately labeled related project stories. Indexed through 11/15/2026, 2:04:58 PM UTC.

No direct repository links were found in the indexed HN discussions over the past seven days. Older discussions are available below.

Mentions over time

HN mentions by year7 dated mentions

Observed mentions: 2016-08-26 22:39:07 UTC to 2021-03-22 14:31:23 UTC.

Counts come from the repository’s dated source evidence. Index cutoff: 2026-11-02 08:16:59 UTC.

View mention counts and date ranges

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Period	Start (UTC)	End (exclusive, UTC)	Mentions	Submissions	Comments
2016	2016-01-01 00:00:00 UTC	2017-01-01 00:00:00 UTC	2	0	2
2017	2017-01-01 00:00:00 UTC	2018-01-01 00:00:00 UTC	1	0	1
2018	2018-01-01 00:00:00 UTC	2019-01-01 00:00:00 UTC	2	1	1
2019	2019-01-01 00:00:00 UTC	2020-01-01 00:00:00 UTC	1	1	0
2020	2020-01-01 00:00:00 UTC	2021-01-01 00:00:00 UTC	0	0	0
2021	2021-01-01 00:00:00 UTC	2022-01-01 00:00:00 UTC	1	0	1

What Hacker News says

7 sources

MrPowers·Mar 22, 2021

Some responses: 1. Yea, but languages that are backwards compatible have libs that are useful for way longer. I can still use Java JAR files that were built with Java 8, and published many years ago. The open source libs get stale so much quicker in Scala. 2. I'd actually argue that Spark is less weird that some other dependencies. If you look at the cats README (https://github.com/typelevel/cats) there is this caveat: Cats relies on improved type inference via the fix for SI-2712, which is not enabled by default. For Scala 2.11.9+ or 2.12 you should add the following to your build.sbt: scalacOptions += "-Ypartial-unification" More cats specific stuff here: https://github.com/sbt/sbt/releases/tag/v1.5.0-RC2 I use Spark a lot so used that for the examples, but think other libs cause even weirder maintenance challenges.

In Scala projects are difficult to maintain

based2·Sep 8, 2019Submission

Cats 2.0.0-RC3

1 points · Open discussion

based2·Sep 13, 2018Submission

Cats 1.4.0 (Scala)

1 points · Open discussion

dtech·Mar 29, 2018

I have no experience with C++, so don't know how it compares. There is some truth in the statement, in that a Scala team will often gradually adapt more advanced features of the language. I wouldn't call them different languages, but rather say Scala is a "Java N+5" in that sense. Java 8 is objectively much more advanced than Java 4, but it's very much the same language and a Java 4 dev will get used to and see value in Java 8's new features. Same with Scala . The main schism is what some people jokingly call the "compiling Haskell with scalac" crowd. They are hardcore functional programmers who value FP ideals like category theory over all else. There even is a forked Scala compiler [1] (luckily the fork and mainline reconciled, and now every change in the fork is a PR for mainline). The crowd is mostly exemplified by libraries like Scal

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aZ [2] and to a lesser extent Cats [3] and shapeless [4]. Some even advocate replacing the whole Scala standard library with their own. Can you at that point still say you're using Scala? You can probably read that I do not personally like that style, and consider it a detriment to the community†, so consider my statements in light of that opinion. The main reason why I don't like the style is that Scala is not powerful enough when compared to Haskell or Julia, requiring lots of magic and boilerplate to make it work. Maybe this will ultimately be resolved, as there have been gradual improvements over versions, and this will be the final niche Scala will occupy long-term, as I have not seen any contenders yet. † I have tremendous respect for the maintainers of the library and their skills, but I don't think the schism is healthy. [1] https://typelevel.org/scala/ [2] https://github.com/scalaz/scalaz [3] https://github.com/typelevel/cats [4] https://github.com/milessabin/shapeless

In Scala Native 0.3.7

aaron-santos·Jun 16, 2017

I'm curious how does this compare to something like Cats' NonEmptyList[1] in Scala? [1] - https://github.com/typelevel/cats/blob/master/core/src/main/...

In Things that Idris improves things over Haskell

yummyfajitas·Aug 27, 2016

It's not a rewriting of history. The dibblegate conflict occurred at the end of 2014. https://groups.google.com/forum/#!topic/scalaz/9X_putSGoCY https://groups.google.com/forum/#!searchin/scalaz/code$20of$... Calling Tony Morris a rapist was probably the highlight of the affair: https://twitter.com/shajra/status/544712807220908032 Up until they realized they couldn't take over the community, Lars Hupel and Miles Sabin had no publicly stated plans to leave Scalaz. Cats initial commit is early 2015. https://github.com/typelevel/cats/commits/master?page=74 I have no idea why everyone dislikes them so much. I use Scalaz, and it's pretty great. From what I've seen Cats is nearly the same thing, I just saw no reason to switch. In what way do you believe Cats is significantly different from Scalaz, beyond the fact that you apparently dislike the

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people involved? Incidentally, scalaz-streaming was also pretty nice - mathematically I liked it but it was simply not as performant as Akka streaming. I'd love to use it if it becomes fast.

In Typelevel Scala

whateveracct·Aug 26, 2016

The overlap between cats and scalaz is gigantic idk why you seem to think they are distinct? I'd bet that the overlap between the most commonly used parts of cats and scalaz is even larger. The main thing scalaz has that cats doesn't is scalaz.concurrent.Task, and there are multiple typelevel-endorsed alternatives to it being worked on as well (in monix and fs2). Task is wonderful btw. fwiw we use scalaz at work and haven't upgraded to cats because it isn't ready. cats just fixed a performance bug that would have destroyed us (Map union mappend was ridiculously unoptimized compared to scalaz's). We .foldMap(/* make a small Map*/) all the time and it's one of our favorite parts of scalaz. see https://github.com/typelevel/cats/issues/1290 for the bug.

In Typelevel Scala